Magnetic separation



April 30, 1968 c F GRAY 3,380,589

MAGNETIC SEPARATION Filed Oct. 23, 1965 FIGURE 2 I 6-6145 //vz7 FlGURE IINVENTOR C F GRAY ATTORNEY KQLMLQQJLWW l S /Lute:

United States Patent 3,380,589 MAGNETIC SEPARATION C F Gray, BatonRouge, La., assignor to Esso Research and Engineering Company, acorporation of Delaware Filed Oct. 23, 1965, Ser. No. 503,106 4 Claims.(Cl. 209-221) ABSTRACT OF THE DISCLOSURE A vertical tubular member withspaced vanes on its inner wall, containing a bed of fluidized materialin its bottom is provided adjacent its upper end with a concentric,external rotatable ring containing opposed pole pieces to separatemagnetic solids from an ascending fluid stream suspension.

This invention relates to the art of separating magnetic particles fromstreams or fluid efiiuents containing magnetic solids particles. Inparticular, it relates to magnetic separators, especially devices usedfor the separation of magnetic and non-magnetic solids particles. Moreparticularly, it relates to an apparatus combination comprising avertically disposed tubular member formed by an enclosing wall, aplurality of spaced vertically aligned vanes attached upon the insidewall, a large diameter ring provided with a plurality of inwardlyprojecting diametrically opposed pole pieces, mounted concentric,external to and rotatable about the tubular member so that the polepieces remain adjacent the external wall of the tubular member wherebymagnetic forces can be intermittently applied to the spaces between thevanes upon rotation of the tubular member. This causes agglomeration ofthe magnetic particles upon application of the magnetic force, andrelease of the agglomerates upon discontinuance of the application ofthe magnetic force to cause descent of the agglomerates, the net effectof which is the stream is denuded of magnetic solids particles. In apreferred embodiment, the tubular member comprises a reactor whichcontains a bed fluidized by gases capable of entraining solids, someportion of which can be removed from the gas by rotation of the ring.

Devices are known which are useful for separating solids particles fromfluids. One Such device, e.g., is the Cottrell precipitator forseparation of fine particles from gaseous streams. In this device, asmoke or flue gas containing solid particles is brought into proximitywith high voltage wires or conduits at different potentials so that thesolids particles become charged and are precipitated out of the gaseousstreams.

Other devices are also known, these including, e.g., those useful forthe separation of magnetic particles from streams containing bothmagnetic and nonmagnetic solids particles. In such devices, strongelectromagnetic fields are produced adjacent to mixtures containingquantities of magnetic ore particles to attract the latter while leavingthe nonmetallic particles in place. These devices have been employed toseparate magnetic particles from streams of particles in either wet ordry state.

While such devices have proven quite adaptable for a variety ofpurposes, there is need for method and apparatus which will provideseparation of magnetic particles from streams or fluid efiiuents,particularly from streams or efliuents which carry both magnetic andnonmagnetic 3,380,589 Patented Apr. 30, 1968 particles. Thus, in certainprocesses gaseous streams are often used to convey mixtures of magneticand nonmagnetic particles, and therein it is desired to separate andremove the magnetic particles from the streams.

In fluidized iron ore reduction processes, e. g., it is often desired toseparate finely divided magnetite (magnetic oxide or iron) or metalliciron particles from effluents leaving the reduction stages of theprocess via the cyclone separators. In such processes, considerableportions of the fines, i.e., particles of about 325 mesh and finer(Taylor screen), are often carried from the process through the cyclone.This represents loss and inefliciency and is a debit to the process.

It is accordingly the object of the present invention to provide methodand apparatus for extracting magnetic solids particles from streams orfluid effiuents, and in particular to extract such particles fromprocess streams, and return these to the process. More particularly, itis an object to provide a magnetic separator device for removal ofmagnetic particles from mixtures of magnetic and nonmagnetic particlescarried or suspended in liquid or gaseous efliuent.

These objects and others are achieved in accordance with the presentinvention which contemplates the steps comprising passing upwardlythrough a zone a fluid stream within which is suspended magnetic solidsparticles, intermittently applying a magnetic force adjacent the zone toretard, hold back, and interrupt the ascent of the magnetic particlesduring application of the magnetic force, and releasing the saidmagnetic particles during null periods or intervals of nonapplication ofthe magnetic force so that the magnetic particles are transported in adirection opposite to that of the moving stream.

In a preferred embodiment the applications of magnetic force are appliedcontinuously, but at different locations around the circumference of thezone so that the net eflect at any given location is that intermittentapplications of magnetic force are simulated.

The invention will be more fully understood by reference to thefollowing detailed description of a specific and preferred embodiment,and to the drawings to which reference is made in the description.

In the drawings:

FIGURE 1 depicts the cross section of a conduit or reactor, or stage ofa reactor, partitioned in part by vertically aligned vanes and withinthe lower portion of which is contained a fluidized bed comprising amixture of magnetic and nonmagnetic solids particles, and through whichbed is passed a fluidizing gas which entrains fines which tend to exitwith the eflluent gas, and in the same figure, in section, and again inFIGURE 2, which is a section AA of FIGURE 1, is shown a cross-section ofa magnetic separator device which is annular to and rotatable about aportion of the reactor.

Referring to the figures is shown a reactor or conduit 10 consisting ofa tubular member 11, the inner circumference or wall 11 of which isaligned with a plurality of vertically aligned vanes or baffles 12through 12 The vertically aligned vanes 12 are perpendicular to theirpoints of contact or connection with the inner wall 11 and are projectedor aligned upon a common center lying at the center or axis of tubularmember 11. The tubular member 11 is constructed of a nonmagneticmaterial.

At the bottom of the tubular member 11 is provided a fluidized bed ofsolids particles of various sizes, some of which are magnetic and somenonmagnetic, and some of which are very finely divided, i.e., 325 meshand finer. The particles are fluidized by gases which enter tubularmember 11 via line 16 and exit via line 17 carrying entrained particles.An overflow line 18 maintains the liquid level of the bed.

A circular holder or ring member 13 is mounted upon the tubular member11 which acts as a hub about which the ring member 13 can be rotated.The annular ring member 13 carries pairs of magnets diametricallyoriented one with respect to another. Thus, upon the interior portion ofannular ring member 13 is mounted a plurality of pole pieces 14, 15.Each member 14, 15 of the pair is located on the opposite sides oftubular member 11, and each member of the pair lies contiguous to theexternal wall surface 11 of tubular member 11. Pole pieces 14, 150ne anorth pole and one a south pole are means for producing a magnetic forceupon the inner wall 11 in the proximity or location of a respectivepolar piece.

The annular ring 13, rotatably mounted via means not shown, provides formovement of pole pieces 14, 15 around tubular member 11 so that themagnetic force therefrom is imparted through the Wall. In removing orextracting metallic particles from an ascending effluent, the magneticfield is constantly moved about tubular member 11 from one contiguouslocation to another so that the effect is to produce an intermittentmagnetic force upon a given sector of inner wall 11 at any particularmoment of time.

In operation, for illustration, it is supposed that annular ring 13 isrotated clockwise as shown in FIG- URE 2. Pole piece 14 thus moves froma space between vertical vanes 12 and 12 to the space between verticalvanes 12 and 12 moves from the space between vanes 12;; and 12 to thespace between 12 and 12 and from the space between vanes 12 and 12 tothe space between vanes 12.; and 12 Simultaneously pole piece 15 movesfrom the space :between vanes 12.; and 12 to the space between vanes 12and 12 from the space between vanes 12 and 12 to the space between vanes12 and 12 and thence to the space between vanes 12 and 12 The movementcontinues ad infinitum while the device is in operation. Simultaneouslywith this rotational movement, a stream of gas is injected into theinterior of tubular member 11 via line 16. The gas ascends through thebed and entrains solids. The solids-laden gas, or efiiuent, whichcontains both magnetic and nonmagnetic particles, ascends through thetubular member 11 and exits there from via line 17. The ascending gasthus entrains both magnetic and nonmagnetic particles on ascent throughthe bed, and the magnetic particles within the gas stream are attractedto the inner wall 11 at location near adjacent pole pieces 14, 15,respectively. The magnetic particles stick to the inner surfaces of thewall 11 at locations between the vanes 12, and their upward movement isrestrained or halted with respect to the gas-solids laden stream. Thus,e.g., magnetic particles stick to the inner wall 11 at locations betweenvanes 12; and 12 and between vanes 12 and 12 As the annular ring 13 isrotated to the next position, however, i.e., as. pole pieces 14, 15 moveto adjacent positions between vanes 12 and 12 and between vanes 12 and12 the pull upon the magnetic particles in the sectors between vanes 12and 12 and vanes 12.; and 12 is released. The fine particles tend toform a very loose agglomerate near the respective sectors of wall 11 andfall back to the bed.

As the magnetic field is moved to any given sector of wall 11 themetallic particles accumulate or loosely agglomerate upon the wall. Asthe magnetic particles tend to follow, e.g., pole piece 14 they arerestrained due to the interference by vanes 12 upon which they impinge.Upon release of the magnetic force, the magnetic particles, now ofhigher effective particle size due to the formation of loose aggregates,fall downwardly and are returned to the bed.

By rotation of the annular ring 13 at suflicient annular velocities, andby use of sufiicient field strengths, the sum total effect is that veryhigh quantities of the magnetic solids particles can be readilyextracted from gas-solids systems and returned to the process.

It is apparent that the effectiveness of the apparatus is dependent tosome extent upon the magnetic field generated by pole pieces 14, 15, bythe number of pole pieces employed in a given device, by the annularvelocity of the pole pieces about tubular member 11, and by the natureof the magnetic material being extracted.

It is obvious, therefore, that the illustrated device is subject tonumerous modifications and changes readily apparent to those skilled inthe art, and therefore the invention should not be limited to the exactconstruction and operation shown and described.

The instant application is found particularly applicable to theextraction, denuding or separation of fines magnetic particles from theprocess streams, i.e, the gaseous effluents of iron ore reductionprocesses. Thus, the invention is specially adaptable to fluidized ironore reduction processes wherein particulate iron oxides are reducedthrough magnetite, or through magnetite and finally to substantiallymetallic iron. This oxide, as well as the metallic iron product, is, ofcourse, magnetic.

The use of the instant device for separating magnetic particles fromsuch process efiluent which contain mixtures of magnetic and nonmagneticparticles is found to be quite practical when the magnetic strength ofthe pole pieces is from about 20 to about 500 gauss, and preferably fromabout 50 to about 200 gauss while providing annular rates ranging fromabout 5 to about 50 revolutions per minute, and preferably from about 10to about 20 revolutions per minute.

The magnetic force is generally intermittently applied upon any givensector at frequencies ranging from about 10 to about cycles, andpreferably from about 20 to about 40 cycles per minute. The rate orfrequency must be adjusted to allow the agglomerated fines to completelydrop out of the magnetic zone. This rate will depend upon the length ofmagnetic zone and the diameter of reactor. Larger diameter reactors willrequire a greater number of vertical vanes.

A rotating or nonrotating member can be employed to provide the magneticfield. Thus, elcctromagnets could as well be distributed around an areaand the individual electromagnets sequentially activated. This wouldprovide the same effect as provided by a rotating member upon which isattached permanent or electromagnets.

Having described the invention, what is claimed is:

1. In apparatus for magnetically separating magnetic solid particlesfrom a fluid stream containing solid particles, the combinationcomprising a vertically disposed tubular member formed by an enclosingwall having an inlet at its bottom end and an outlet at its top end, aplurality of spaced vertically aligned vanes attached parallel to theinside walls at the location of contact and aligned upon a common centerlying at the axis of said tubular member, a large diameter ring providedwith a plurality of inwardly projecting diametrically opposed polepieces, means to move said stream upwardly in the tubular member fromthe bottom of said member to a region adjacent said ring, said polepieces being mounted concentric, external to and rotatable about thetubular member so that the pole pieces remain adjacent the external wallof the tubular member whereby magnetic force can be intermittentlyapplied to the spaces between the vanes upon rotation of the tubularmember to cause agglomeration of the magnetic particles upon applicationof the magnetic force, and release of the agglomerates upondiscontinuance of the application of the magnetic force to cause theirdescent, the net eifect of which is that said stream is denuded ofmagnetic solid particles.

2. The apparatus of claim 1 wherein the wall of the tubular member isconstructed of nonmagnetic material.

3. The apparatus of claim 1 wherein the tubular member constitutes areactor Within which can be contained a bed fluidized by gases capableof entraining solids.

4. The apparatus of claim 1 wherein two pole pieces are mounted on theinside of the ring.

References Cited UNITED STATES PATENTS Wedge 209-232 Fernow 209-215 Latz2092l5 Clute 209-214 HARRY B. THORNTON, Primary Examiner. 10 R. HALPER,Assistant Examiner.

